Catechism of the Catholic Church
1425 "You were washed, you were sanctified, you were justified in the name of the Lord Jesus Christ and in the Spirit of our God." 9 One must appreciate the magnitude of the gift God has given us in the sacraments of Christian initiation in order to grasp the degree to which sin is excluded for him who has "put on Christ." 10 But the apostle John also says: "If we say we have no sin, we deceive ourselves, and the truth is not in us." 11 And the Lord himself taught us to pray: "Forgive us our trespasses," 12 linking our forgiveness of one another's offenses to the forgiveness of our sins that God will grant us.
1426 Conversion to Christ, the new birth of Baptism, the gift of the Holy Spirit and the Body and Blood of Christ received as food have made us "holy and without blemish," just as the Church herself, the Bride of Christ, is "holy and without blemish." 13 Nevertheless the new life received in Christian initiation has not abolished the frailty and weakness of human nature, nor the inclination to sin that tradition calls concupiscence, which remains in the baptized such that with the help of the grace of Christ they may prove themselves in the struggle of Christian life. 14 This is the struggle of conversion directed toward holiness and eternal life to which the Lord never ceases to call us. 15
English Translation of the Cathechism of the Catholic Church for the United States of America © 1997, United States Catholic Conference, Inc.